Known manual pumps of the aforesaid type comprise a relatively large number of parts, they therefore being of complicated assembly and requiring a lengthy time for their fitting.
The unidirectional valve means used in known pumps are generally of the ball type, these also being of relatively difficult assembly. Moreover in known pumps separate ball valves must be provided for the entry and exit of the pumped lubricant.
In some known pumps, the piston drive rod also acts as the conveying channel for the pumped lubricant, so further complicating the pump construction.